Sand control method employing asphaltenes

ABSTRACT

This invention relates to a method for treating wells completed in subterranean formations which contain unconsolidated sand particles, so as to form a permeable barrier which will permit the flow of liquids therethrough while restraining the flow of the unconsolidated sand particles into the well bore. The method comprises saturating sand adjacent the well bore to be treated with petroleum having a high asphaltic content and optionally thereafter contacting the asphaltic petroleum with a solvent capable of solubilizing non-asphaltic fractions of the petroleum and precipitating or causing deposition of the asphaltic or bituminous portions of the petroleum. A heated fluid such as steam is thereafter injected into the formation to cause solidification of the asphaltic materials which effectively binds the sand grains together to form a porous mass which will effectively restrain the movement of sand particles in the well bore upon subsequently placing the well on production. Suitable hydrocarbon materials for causing precipitation of the asphaltic or bituminous portions of the petroleum include liquid paraffinic hydrocarbons such as butane, pentane, or hexane, N-methyl-2pyrrolidone and furfural. Steam or a mixture of steam and noncondensable gas such as nitrogen, or mixture of steam and air are then injected into the formation to dehydrate and otherwise solidify the precipitated asphaltic material.

United States Patent [191 Wu et al.

[451 Oct. 7, 1975 SAND CONTROL METHOD EMPLOYING ASPHALTENES [75]Inventors: Ching H. Wu; Alfred Brown; Daniel T. Konopnicki, all ofHouston, Tex.

[73] Assignee: Texaco Inc., New York, NY.

[22] Filed: July 25, 1974 [21] Appl. No.: 491,985

[52] US. Cl. 166/276; 166/288 [51] Int. Cl. E2113 43/04 [58] Field ofSearch 166/276, 278, 288, 294

[56] References Cited UNITED STATES PATENTS 2,187,895 1/1940 Sanders166/276 2,427,848 9/1947 Garrison 166/294 2,670,047 2/1954 Mayes et al..166/262 2,771,952 11/1956 Simm 166/276 X 3,003,555 10/1961 Freeman etal. 166/288 3,093,192 6/1963 Allen 166/294 3,180,415 4/1965 Allen166/294 3,182,722 5/1965 Reed..... 166/288 X 3,323,591 6/1967 Harvey166/262 3,559,736 2/1971 Bombardieri 166/276 3,812,913 5/1974 Hardy etal. 166/288 [57] ABSTRACT This invention relates to a method fortreating wells completed in subterranean formations which containunconsolidated sand particles, so as to form a permeable barrier whichwill permit the flow of liquids therethrough while restraining the flowof the unconsolidated sand particles into the well bore. The methodcomprises saturating sand adjacent the well bore to be treated withpetroleum having a high asphaltic content and optionally thereaftercontacting the asphaltic petroleum with a solvent capable ofsolubilizing nonasphaltic fractions of the petroleum and precipitatingor causing deposition of the asphaltic or bituminous portions of thepetroleum. A heated fluid such as steam is thereafter injected into theformation to cause solidification of the asphaltic materials whicheffectively binds the sand grains together to form a porous mass whichwill effectively restrain the movement of sand particles in the wellbore upon subsequently placing the well on production. Suitablehydrocarbon materials for causing precipitation of the asphaltic orbituminous portions of the petroleum include liquid paraffinichydrocarbons such as butane, pentane, or hexane, N-methyl-2-pyrrolidoneand furfural. Steam or a mixture of steam and non-condensable gas suchas nitrogen, or mixture of steam and air are then injected into theformation to dehydrate and otherwise solidify the precipitated asphalticmaterial.

U.S. Patent Oct. 7,1975

SAND CONTROL NIETHOD EMPLOYING ASPHALTENES BACKGROUND OF THEINVENTION 1. Field of the Invention This invention pertains to a methodfor treating wells penetrated and completed in subterranean earthformations, and more particularly to a method for treating a petroleumcontaining formation in the immediate vicinity of the well so as tostabilize unconsolidated sand and prevent their migration into or awayfrom the well. Still more particularly, this invention pertains to amethod for treating such wells with granular materials saturated withbitumen or bituminous or asphaltic petroleum, contacting the materialwith a low molecular weight asphaltic or paraffmic hydrocarbon orN-methyl-Z-pyrrolidone or furfural to cause precipitation of asphalt,and then introducing steam to solidify the bitumen and bind the sandgrains together.

2. Prior Art and Background Recovery of formation fluid such aspetroleum from a subterranean formation is frequently difficult when thesubterranean formation is comprised of one or more incompetent orunconsolidated sand layers or zones. The sand particles in theincompetent or unconsolidated sand zone move or migrate into the wellbore during recovery of formation fluids from that zone, or sandparticles move away from the well during injection of secondary ortertiary recovery fluids into the formation. In the instance ofrecovering the fluid from the formation, the movement of sand into thewell bore can cause the well to cease production of fluids therefrom.Also, small sand particles can plug small openings and porous massesformed around the well bore for the purpose of restraining the flow ofsand, such as screens or slotted liners which are frequently placed inwells for this purpose. Not only can fluid production be reduced or evenstopped altogether, if sand particles flow through the well to thesurface, considerable mechanical problems can result from passage ofabrasive sand particles through pumps and other mechanical devices.

Many techniques have been described in the prior art for preventing ordecreasing the flow of sand into well in a course of petroleumproduction, including the use of sand screens, filters, perforated orslotted liners, etc. around the well. These prior art attempts have beensuccessful in some limited instances, but have not always been entirelysatisfactory for a number of reasons. Mechanical devices usuallyrestrain only the larger particle sand and are not completely effectivefor the purpose of restraining or preventing the flow of fine particlesfrom the formation into the well and ultimately to the surface:Furthermore, the devices interfere with various types of completions andwork over operations.

Recently, there have been introduced into the market place by numerousoil field companies, chemical compositions which bond the sand grainstogether with a resinous plastic material to form a permeable mass whicheffectively restrains the flow of sand particles from the formation.These methods involve injecting into a sand pack around a well bore, apolymerizable, resinous material, which is later caused to polymerize soas to consolidate formation sand or sand packed around the well for thatpurpose, to form the desired permeable barrier. Numerous difficultieshave been encountered in commercial application and use of thistechnique, including the difficulty of achieving the even polymerizationof the resinous material to the degree necessary to consolidate the sandparticles while still maintaining the necessary permeability so thatpetroleum or other fluid may pass therethrough. Furthermore, theresinous materials are expensive. Recently, many tertiary recoverytechniques involving the injection of steam or other fluids into theformation for the purpose of mobilizing viscous petroleum, and this hasimposed a still greater burden on sand consolidation techniques, and hasparticularly caused problems with the plastic consolidation techniqueswhich are sensitive to the high temperature, high pH aqueous fluidsfrequently employed in such processes. The resinous materials arefrequently dissolved or degraded by contact with the hot alkaline fluidsused in tertiary recovery processes.

In view of the foregoing discussion, it can be appreciated that there isa substantial, unfulfilled need for a sand control method capable ofpreventing the flow of unconsolidated sand particles into a well boreduring periods of oil recovery or away from a well bore during periodsof injection of fluids thereinto. More particularly, there is a need forinexpensive, reliable method of consolidating sand in a formation havingan appreciable quantity of unconsolidated sand, which will result in theformation of a permeable mass that will not be adversely affected bysubsequent contact with high temperature, alkaline fluid such as steamor caustic.

By the method of the present invention one is able to treat undergroundformations so as to effect the solidation of granular materials such assand or gravel into a permeable mass which will effectively restrain themovement of unconsolidated sand particles, which permeable mass will notbe appreciably degraded by subsequent contact with hot alkaline fluidssuch as steam an'd/or caustic. and generally avoid many of thedisadvantages of prior art methods, both mechanical and chemical.

SUMMARY OF THE INVENTION We have discovered that a permeable mass may beformed, which permeable mass is relatively insensitive to thermal fluidsand can be employed in connection with thermal recovery processes,involving the precipitation of asphaltic material from asphalticpetroleum such as bituminous petroleum, onto sand grains located aroundthe well bore by introduction of a suitable asphalt precipitatingsolvent into the vicinity of the well bore, after which a hot fluid suchas steam is introduced to volatilize the solvent and other volatilefractions existing in the vicinity of the well bore and harden theasphaltic material to form a permeable, competent mass, bonding the sandgrains together. In some application such as, for example, tar sanddeposits, naturally occurring unconsolidated sand and naturallyoccurring bituminous petroleum may be utilized as the reactants. Inother applications, the well bore may be enlarged and suitable sand orother granular material packed into the well bore around the productiontubing. The sand is then saturated with asphaltic or bituminouspetroleum by several means. The asphalt precipitating solvent is thenintroduced into the mixture of sand and asphaltic petroleum which causesdeposition or precipitation of the asphaltic material onto the sandgrain. Steam is then introduced into the zone to volatilize certainfractions remaining and to solidify the asphalt or bitumen so as toeffectively bind the sand grains together. Suitable solvents for causingdeposition of the asphaltic material include liquid aliphatic orparaffinic hydrocarbons such as pentane, hexane, etc., as well asN-methyl- 2-pyrrolidone or furfural. The steam which is introduced intothe precipitated asphalt and sand zone may be saturated or super heated,and optionally may contain a non-condensable gas such as nitrogen or airto aid in maintaining the desired permeability. The permeable solid thusformed is mechanically stable, per mits petroleum or other formationfluids to flow therethrough, and resists the detrimental effect of hotalkaline fluids which may be employed in subsequent oil re coveryoperations.

BRIEF DESCRIPTION OF THE DRAWING The attached drawing illustrates a wellin a tar sand deposit being subjected to the method of our invention forforming a sand restraining, permeable mass around the well bore.

DETAILED DESCRIPTION OF THE INVENTION AND DESCRIPTION OF THE PREFERREDEMBODIMENTS Briefly, the process of our invention comprises thefollowing steps, which will be described more fully below:

I. Positioning the sand in the well bore and 2. Saturating the sand withbituminous, asphaltic petroleum 3. lntrouction of the asphaltprecipitating solvent into the sand-bitumen mass, and

4. Introduction of steam into the bitumen-sand mass to causesolidification of the bitumen or asphaltic material to bind the sandgrains together.

I. PLACING THE SAND IN THE WELL BORE According to one aspect of ourinvention, the sand naturally occurring in the formation, such as forexample, in a tar sand deposit, may be utilized for the sand in theformation of the sand restraining, permeable mass according to theprocess of our invention. Accordingly, one embodiment of the process ofour invention involves simply intoducing an asphaltic or bituminouspetroleum into an unconsolidated sand naturally occurring in theformation to saturate or essentially saturate the same with asphaltic orbituminous petroleum.

In many applications of the process of our invention, the subterraneanformation does not contain adequate sand for use in the formation of thepermeable barrier, or else the sand particle size or othercharacteristics are not suitable for use in the formation of thebarrier. In

those cases it is necessary to introduce sand into the formation for thepurpose of forming the permeable barrier.

There are several methods for placing the granular material adjacent theformation in which the sand restraining permeable mass is to be formed.In one embodiment of the process of our invention, a minor amount of theformation adjacent the well to be treated is removed by washing withwater or other suitable fluid or by under-reaming to form a small cavityin the immediate vicinity of the well bore. After a suitable amount ofmaterial has been removed therefrom, the tubing string or other wellhardware is placed in the well, and sand or gravel is placed into thewell bore.

One suitable method for accomplishing this is to form a slurry of thegranular material in water or some other suitable fluid and pump theslurry into the well bore.

The above described procedure may better be understood by reference tothe attached figure, in which tubing 1 having perforations near thelower end thereof 2 is contained in well casing 3. The formationmaterial is removed adjacent the petroleum formation to form a cavity 4which extends outward a small distance from the well bore. The granularmaterial is slurried in fluid; for example, the sand may be slurried inwater or water containing other agents, and injected into the annularspace 5 between tubing 1 and casing 3. The slurry then passes throughthe bottom of the annular space, and then through slots 2 into theproduction well bore where it is pumped to the surface of the earththrough the tubing. The granular material filters against the formationand also against the perforations 2 in the production tubing 1, forminga closely packed mass 6 which consists essentially of the granularmaterial packed tightly together. This process is continued until themass of granular material extends to a point above the top of theperforations 2 and preferably some distance thereabove so that if anyshrinkage occurs in subsequent treatment steps, the cavity adjacentperforations 2 will still be completely filled with granular material.

If the sand restraining permeable mass is to be formed from sand orother granular material other than naturally occurring into theformation, the optimum results are obtained at the sand particles sizemeet certain specific requirements. The sand or other granular materialshould be selected from the broad range of from about 10 to about mesh,and preferably should be closely spaced within that broad range so thatthe larger particle sizes utilized are no more than approximately twicethe smallest particle sizes employed. For example, sand in the range of10 to 20 mesh, or 20 to 40 mesh, or 40 to 80 mesh, may be utilizedeffectively. The reason for this optimum size is that sand particlescoarser than about 10 mesh when bonded together according to the processto be described in detail below, result in the formation of a permeablemass whose low channels or pore sizes are so great that fine sandparticles can move freely therethrough in the production well. Very finesand particles, i.e. those particles finer than about 80 mesh, areunsuitable because the resultant barrier had insufficient permeabilityto permit the flow of formation fluids therethrough. From thisdiscussion it can be appreciated that the type of sand present in theformation which the permeable barrier is to restrain the movement ofwill to some degree influence the especially preferred particle size ofthe sand to be introduced into the formation. Thus if very fine sand ispresent in the formation, then the best result will be attained usingsand within the finer range, ie from about 40 to about 80 mesh.Similarly, higher production rates can safely be attained in formationswhose naturally occurring sand is relatively coarse by means of usingthe coarser sand grains within the specified range, such as for example10 to 20 mesh or 20 to 40 mesh sand.

II. INTRODUCTION OF THE ASPHALTIC OR BITUMINOUS PETROLEUM INTO THE SANDAccording to one aspect of our invention, the asphaltic or bituminouspetroleum naturally occurring in a formation may be utilized as thesource of the asphaltic material to form the sand restraining permeablemass. That is to say, if the naturally Occurring formation petroleum ishighly asphaltic or bituminous, this may be utilized as a part or all ofthe asphaltic petroleum or formation of the permeable In some instancesit is not necessary to add any additional asphaltic petroleum, whereasin others it may be necessary to increase the asphaltic petroleumsaturation within this'portion of the formation immediately adjacent tothe well to be treated, so that a stable barrier may be formed. 7

When it is desirable to enlarge the cavity and introduce sand ratherthan use naturally occurring formation sand, it will generally benecessary to also introduce the asphaltic or bituminous petroleum. Itshould be realized that asphaltic or bituminous petroleum is generallyvery viscous, and so ordinarily cannot be simply pumped into the sandpack. The viscosity of bituminous petroleum such as is found in tar sanddeposits, for example, is in the range of millions of centipoise atformation temperature. The viscosity-temperature relationship of suchpetroleum is exceedingly sharp, however, and the viscosity of tar sandmaterial drops to a value of only a few centipoise at about 300F.Acordingly, one method of introducing the bituminous petroleum into thesand pack is simply to heat the petroleum to a temperature of at least200F and preferably around 300F, so as to make the bituminous petroleumpumpable, and introduce the hot bituminous petroleum into the sand pack.It is preferable to preheat the sand pack to a similar temperature, sothat the petroleum will not cool too rapidly, and thus the sand pack maybe saturated uniformly into the desired depth away from the well bore.The sand pack may be conveniently preheated by passing a heated fluidsuch as steam through the sand pack prior to introduction ofa heatedbituminous petroleum into the sand pack.

Another method for coating the granular material with bituminouspetroleum involves the formulationof an oil-in-water emulsion which hasa much lower viscosity than the petroleum itself. The desired emulsionmay be formed by mixing a quantity of bituminous petroleum with water,the ratio of oil to water being from about 1.0 to about 0.01 andpreferably about 0.10. The formulation of the emulsion is aided byinclusion of a small amount of an alkalinity agent such as sodiumhydroxide in the water. Generally from about 0.01 to about 1 percent byweight sodium hydroxide is satisfactory for this purpose.

After the bituminous petroleum and water emulsion has been formulated,it may easily be pumped down the tubing and/or annular space between thetubing and casing, into the granular material adjacent to theperforations in the production tubing. The sand pack should be throughlysaturated with the bitumen and water emulsion. An acid such hydrochloricacid or sulfuric acid may then be introduced into the saturated sandpack to break the emulsion or resolve it into its separate phases. Thevolume of acid needed to treat the emulsion-saturated sand pack willgenerally be from about 1 percent .toabout 50 percent of the volume ofemulsion present. The concentration of acid may be from about 1 percentto about 10 percent by weight. When the acid contacts the emulsion andresolves it into its phases, the viscous bituminous petroleum depositson the sand grains, and the water phase may easily be displaced out ofthe pack either into the formation or into the well bore and produced tothe surface of the earth.

Still another method for saturating the sand pack with bituminouspetroleum comprises forming a solution of the bituminous petroleum and asuitable solvent such as benzene, toluene and naphtha so as to form alow viscosity solution, and then pump the solution into the sand packthrough the tubing or annular space or both. A suitable gas such as air,nitrogen or carbon dioxide or natural gas may then be passed through thesand or gravel pack to vaporize the solvent, leaving the viscouspetroleum deposited on the sand or gravel. The vaporization may beaccelerated if an inner gas such as nitrogen is heated to a temperaturewell above the boiling point of the solvent prior to passing the gasthrough the sand pack.

III. ASPHALT PRECIPITATING SOLVENT INJECTION After the asphaltic orbituminous petroleum has been placed in the 'pore space of the sand orgranular material pack adjacent the'well bore, a solvent capable ofsolubilizing the non-asphaltic or non-bituminous fraction of thepetroleum, and causing precipitation or deposition of the asphaltic orbituminous fraction of the petroleum on the granular material grainsshould be introduced into the formation. The solvent may be a lowmolecular weight hydrocarbon, preferably a paraffinic hydrocarbon havingfrom three to ten carbon atoms such as pentane or hexane. The paraffinichydrocarbon should be introduced into the formation under temperatureand pressure conditions which will result in it entering the sand packin a liquid form. Accordingly, the temperature should be below about 250and preferably about in order to insure that it is essentially all inthe liquid phase of the temperature existing in the sand pack beingtreated. In deeper deposits, which can tolerate higher injectionpressures, lower molecular weight paraffinic hydrocarbons such as'butaneor even propane may be utilized effectively, so long the temperature andpressure at which the materials are injected are such that the fluidwill enter the formation a liquid.

Another suitable asphalt precipitating solvent for use isN-methyl-2-pyrrolidone whose formula is as follows:

This material should similarly be introduced into the formation in theform of a liquid, in order to insure that it effectively precipitatesmost of the bituminous or asphaltic material present in the sand pack.

Still another solvent suitable for use in the process of our inventionfor the purpose of precipitating asphalt is furfural, whose formula isas follows:

A mixture of any two or more of the above materials may also be usedeffectively to precipitate the asphaltic or bituminous petroleumfraction of the petroleum.

IV. SOLIDIFICATION OF THE ASPHALT OR BITUMEN After the asphaltic orbituminous fraction of the petroleum has been precipitated by suitabletreatment as described immediately above, the final phase of the processfor forming the sand controlled permeable barrier is to introduce aheated fluid, preferably a heated gaseous fluid into the sand pack tovaporize volatile materials present and solidify the asphaltic orbituminous material. Steam is an especially preferred fluid for thispurpose, since it is inexpensive and readily available, and equipmentfor generating steam will frequently be available in the oil field forthe thermal recovery stimulation process to be applied later.

Either saturated or super heated steam may be utilized in this step,although ordinarily the preferred embodiment will be to utilizesaturated steam because it is less expensive and quite satisfactory forthis purpose. So long as the temperature of the sand pack is raised toat least 250F, the desired solidification of the deposited asphalt willbe achieved. It is preferred that the steam temperature be at least 300Fin order to effectively solidify the asphaltic materials in a reasonablyshort period of time. Ordinarily, the time required for thesolidification stepwill be inversely related to the temperature. Thus,if lower temperature fluids are utilized to heat and solidify theasphaltic material, a longer period of time will be required. If thesteam is at least 300F, the desired solidification occurs within only afew hours. Ordinarily from about 1 to about 12 hours is sufficient tosolidify the deposited asphaltic material. Although longer exposure tosteam will not be detrimental to the process, and may be utilized ifdesired, there is no particular advantage to injecting steam into thesand pack for any period of time longer than is necessary to achieve thedesired solidification of the asphaltic material.

Any other heated gaseous material may be utilized for the solidificationstep. For example, air or nitrogen or any other suitable gas may beheated to a temperature of around 300F and passed through the sand packto effectively solidify the asphaltic materials and bind the loose sandgrains together.

V. FlELD EXAMPLE The process of our invention may better be understoodby reference to the following pilot field example, which is offered onlyas a preferred illustrative embodiment, and is not intended to belimitative or restrictive of our invention.

A tar sand deposit is to be subjected to steam emulsification drive. Awell is drilled into the tar sand deposit, which is located under anoverburden whose thickness is about 300 feet and the tar sand depositthickness is around 75 feet. The tar sand deposit immediately adjacentto the well is under-reamed to create a cavity approximately 3 feet indiameter extending the full 75 foot thickness of the tar sand deposit. Acasing is run to the top of the tar sand deposit and a production tubingstring is run to the bottom of the tar sand deposit. Perforations areformed over the full 75 foot interval, since it is desired to introducefluids essentially uniformly into the tar sand interval.

A slurry is formed of 40 to mesh frac sand in water, and this slurry ispumped into the annular space. Water is pumped from the productiontubing, to cause the sand grains to pack closely around the perforatedproduction tubing and to form thereby a dense sand pack whichsubstantially fills the cavity around the well. This is continued untilcalculations indicate that the sand pack is about 1 foot above the topof the perforation.

Prior to introduction of the bituminous petroleum, steam at atemperature of 300F is pumped into the production tubing to contact thesand pack and heat the sand grains contained therein near a temperaturenear 300. Passage of steam therethrough for about 2 hours is sufficientto heat the sand grains.

A quantity of bituminous petroleum obtained from the tar sand materialsimilar to that found in the formation is heated to a temperature of300F and introduced into the production string, where it flows outthrough the perforations and saturates the sand grains. Since theporosity of the sand pack is approximately 20 percent, the volume to besaturated with bituminous petroleum is (3/2) X 11- X 75 X 0.20 cubicfeet, which is the amount of bituminous petroleum to be introduced intothe tubing string to saturate the sand pack. Approximately 10 percentexcess is' utilized to assure that good contact between all of the sandand bituminous petroleum is achieved.

Air is slowly passed down the production tubing to cool the bituminouspetroleum and sand to about 100 prior to the next step, so that theasphalt participating solvent will not be vaporized upon contacting thehot material.

Hexane is chosen as the asphalt precipitating solvent, since it is notdesired to exceed the overburden-related pressure limitation and sinceit is necessary that the solvent enter this sand pack in a liquid form.Approximately 50 gallons of hexane is pumped slowly into the injectiontubing. During this time the annular space is closed off so the hexanewith portions of the petroleum dissolved therein will enter theformation rather than pass back up the tubing. After the hexane has beenpumped into the sand pack, steam at a temperature of 325 is introducedinto the sand pack for approximately 6 hours so as to solidify theprecipitated asphalt, to bind the sand grains together and form thedesired permeable mass for sand control purposes.

The well treated according to the above discussion is utilized as theproduction well and the subsequently applied steam-emulsification driveprocess, and no problems are encountered in connection with movement ofunconsolidated sand into the well bore, and further that the permeablemass formed in accordance with the above described procedure is notaffected by subsequent contact with steam and caustic.

Vl. EXPERIMENTAL SECTION The following laboratory experiments wereperformed to verify the operability and determine the effectiveness ofthe process of our invention. A linear laboratory cell approximately 7inches in length and 1.4 inches in diameter was packed with a sample ofathabasca tar sand to a density of 1.8 grams per cubic centimeter. Atotal of cubic centimeters of liquid normal butane was injected into thesand pack in 5 slugs averaging 29 cubic centimeters per slug, each slugbeing depleted by normal butane vapor pressure. Steam at a temperatureof 294F was then introducd into the cell to displace the oil. Aftercompletion of this experiment, the contents of the cell was examined andit was noted that the 3 inches into the cell from the point of injectionwas consolidated by dark precipitates, and the portion immediatelyadjacent to the injection well was very well consolidated and permeable.

Thus we have disclosed and demonstrated that a sand controllingpermeable mass may be formulated by con-- tacting a mixture of sand andasphaltic or bituminous petroleum, which may be naturally occurring ormay be placed in the well bore for the purpose of forming the permeablemass, by contacting same with an effective asphalt precipitating solventsuch as a liquid paraffinic hydrocarbon, as well as with furfural orN-methyl-2- pyrrolidone, and thereafter introducing steam or any otherheated fluid into the zone for the purpose of dehydrating andsolidifying the asphaltic material. The asphaltic material binds thesand grains together, forming a permeable mass which will effectivelyrestrain the flow of sand into the well. bore during periods of recoveryof fluid therefrom.

While our invention has been disclosed in terms of a number ofillustrative embodiments, it is not so limited since many variationsthereof will be apparent to persons skilled in the art without departingfrom the true spirit and scope of our invention. Similarly, whilereactions and mechanisms have been proposed to explain the benefitsresulting from the application of the process of our invention, it isnot necessarily hereby represented that these are the only or even theprincipal reactions and mechanisms occurring, and we do not wish to bebound by any particular mechanism or reaction. It is our intention thatour invention be limited and restricted only by those limitations andrestrictions as appear in the claims appended immediately hereinafterbelow.

We claim:

1. A method of treating a subterranean unconsolidated sand and petroleumcontaining formation penetrated by at least one well, said well being influid communication with the subterranean formation, for the purpose offorming a permeable barrier around the well to restrain the movement ofsand particles while permitting the passage of petroleum therethrough,comprising:

a. introducing a pre-determined quantity of granular material into thewell bore adjacent the formation;

b. introducing bituminous petroleum into the granular material;

c. introducing an asphalt precipitating solvent selected from the groupconsisting of paraffinic hydrocarbons having from 3 to 10 carbon atoms,furfural, N-methyl-Z-pyrrolidone, and mixtures thereof; and

d; introducing a heated fluid into the granular material at atemperature of at least 250F to solidify the precipitated asphalt.

2. A method as recited in claim 1 wherein the granular material is sand.

3. A method as recited in claim 2 wherein the particle size of the sandis from about 10 to about mesh.

4. A method as recited in claim 3 wherein the particles size of thelargest sand grain contained therein is not more than twice the particlesize of the small sand grain contained therein.

5. A method as recited in claim 1 wherein the particulate mattersintroduced into the well bore by forming a slurry of particulate matterand fluid and pumping the slurry into the well, so that the particulatematter forms against the face of the formation.

6. A method as recited in claim 1 wherein the asphalt precipitatingsolvent is hexane.

7. A method as recited in claim 1 wherein the asphalt precipitatingsolvent is pentane.

8. A method as recited in claim 1 wherein the asphalt precipitatingsolvent is furfural.

9. A method as recited in claim 1 wherein the asphalt precipitatingsolvent is N-methylQ-pyrrolidone.

10. A method as recited in claim 1 comprising the additional initialstep of removing a portion of the formation immediately adjacent to thewell bore to form a cavity.

11. A method recited in claim 10 wherein the formation material isremoved by washing with a liquid.

12. a method as recited in claim 10 wherein the formation is removed bymechanical reaming.

1. A METHOD OF TREATING A SUBTERRANEAN UNCONSOLIDATED SAND AND PETROLEUMCONTAINING FORMATION PENETRATED BY AT LEAST ONE WELL, SAID WELL BEING INFLUID COMMUNICATION WITH THE SUBTERRANEAN FORMATION, FOR THE PURPOSE OFFORMING A PERMEABLE BARRIER AROUN THE WELL TO RESTRAIN THE MOVEMENT OFSAND PARTICLES WHILE PERMITTING THE PASSAGE OF PETROLEUM THERETHROUGH,COMPRISING, A. INTRODUCING A PRE-DETERMINED QUANTITY OF GRANULARMATERIAL INTO THE WELL BORE ADJACENT THE FORMATION, B. INTRODUCINGBITUMINOUS PETROLEUM INTO THE GRANULAR MATERIAL, C. INTRODUCING ANASPHALT PERCIPITATING SOLVENT SELECTED FROM THE GROUP CONSISTING OFPARAFFINIC HYDROCARBONS HAVING FROM 3 TO 10 CARBON ATOMS, FURFURAL,N-METHYL-2-PYRROLIDONE, AND MIXTURES THEREOF, AND D. INTRODUCING AHEATED FLUID INTO THE GRANULAR MATERIAL AT A TEMPERATURE OF AT LEAST250*F TO SOLIDIFY THE PERCIPITATED ASPHALT.
 2. A method as recited inclaim 1 wherein the granular material is sand.
 3. A method as recited inclaim 2 wherein the particle size of the sand is from about 10 to about80 mesh.
 4. A method as recited in claim 3 wherein the particles size ofthe largest sand grain contained therein is not more than twice theparticle size of the small sand grain contained therein.
 5. A method asrecited in claim 1 wherein the particulate matters introduced into thewell bore by forming a slurry of particulate matter and fluid andpumping the slurry into the well, so that the particulate matter formsagainst the face of the formation.
 6. A method as recited in claim 1wherein the asphalt precipitating solvent is hexane.
 7. A method asrecited in claim 1 wherein the asphalt precipitating solvent is pentane.8. A method as recited in claim 1 wherein the asphalt precipitatingsolvent is furfural.
 9. A method as recited in claim 1 wherein theasphalt precipitating solvent is N-methyl-2-pyrrolidone.
 10. A method asrecited in claim 1 comprising the additional initial step of removing aportion of the formation immediately adjacent to the well bore to form acavity.
 11. A method as recited in claim 10 wherein the formationmaterial is removed by washing with a liquid.
 12. a method as recited inclaim 10 wherein the formation is removed by mechanical reaming.